Spaceweather.com posts daily satellite images of noctilucent clouds (NLCs), which hover over Earth's poles at the edge of space. The data come from NASA's AIM spacecraft. The north polar "daisy" pictured below is a composite of near-realtime images from AIM assembled by researchers at the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP).

Geomagnetic Storms:Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm

Updated at: 2013 Dec 11 2200 UTC

Mid-latitudes

0-24 hr

24-48 hr

ACTIVE

05 %

45 %

MINOR

01 %

30 %

SEVERE

01 %

05 %

High latitudes

0-24 hr

24-48 hr

ACTIVE

15 %

05 %

MINOR

15 %

20 %

SEVERE

05 %

70 %

Wednesday, Dec. 11, 2013

What's up in space

When is the best time to see auroras? Where is the best place to go? And how do you photograph them? These questions and more are answered in a new book, Northern Lights - a Guide, by Pal Brekke & Fredrik Broms.

HERE COME THE GEMINIDS: Earth is entering a stream of debris from rock comet 3200 Phaethon, source of the annual Geminid meteor shower. Forecasters expect the shower to peak on Dec. 13-14 with as many as 120 meteors per hour. Lunar interference will be a problem, as glare from the nearly-full Moon reduces the number of visible meteors 2- to 5-fold. You can listen to radar echoes from the Geminids, unaffected by moonlight, on Space Weather Radio. Also, tune into NASA's live web chat about the Geminids on Friday the 13th beginning at 11 pm EST.

CORONAL HOLE: NASA's Solar Dynamics Observatory is monitoring a large coronal hole in the sun's northern hemisphere. Shown here in an extreme ultraviolet photo taken during the early hours of Dec. 11th, the UV-dark chasm overlies more than 500 billion square kilometers of solar terrain:

Coronal holes are places in the sun's atmosphere where the magnetic field opens up and allows solar wind to escape. A broad stream of solar wind flowing from this particular coronal hole should reach Earth on Dec. 15-17.

The last time a solar wind stream blew past Earth, on Dec. 7th, the impact sparked Northern Lights in the United States as far south as Montana and Michigan. A repeat performance could be in the offing. High-latitude sky watchers should be alert for auroras early next week. Aurora alerts:text, voice

ELECTRIC-BLUE CLOUDS OVER ANTARCTICA: The season for noctilucent clouds has begun in the southern hemisphere. NASA's AIM spacecraft is monitoring a vast bank of rippling electric-blue NLCs blanketing almost all of Antarctica. This two week movie chronicles the onset of the clouds in late November and their rapid spread into December:

NLCs are Earth's highest clouds. Seeded by "meteor smoke," they form at the edge of space 83 km above Earth's surface. When sunlight hits the tiny ice crystals that make up these clouds, they glow electric blue.

NLCs appear during summer because that is when water molecules are wafted up from the lower atmosphere to mix with the meteor smoke. That is also, ironically, the time when the upper atmosphere is coldest, allowing the ice crystals of NLCs to form.

In recent years NLCs have intensified. Some researchers believe this is a sign of climate change. One of the greenhouse gases that has become more abundant in Earth's atmosphere since the 19th century is methane. "When methane makes its way into the upper atmosphere, it is oxidized by a complex series of reactions to form water vapor," explains Hampton University Professor James Russell, the principal investigator of AIM."This extra water vapor is then available to grow ice crystals for NLCs."

COMET ISON UPDATE: Later this month, NASA plans to point the Hubble Space Telescope at Comet ISON to see if anything remains after the comet's death plunge through the sun's atmosphere on Nov. 28th. Note to Hubble: Don't expect to see much. Amateur astronomers are already searching the comet's position and setting hard limits on the brightness of any remains. Consider this image taken on Dec. 8th by Eric Allen of the Observatoire du Cégep de Trois-Rivières in Champlain, Québec:

The position of the comet--had it survived--is circled. "I unfortunately have to say that there is nothing down to about magnitude +16.5, not even a small condensation," says Allen. More information about Allen's observing techniques and image processing may be found here.

As Karl Battams of the Naval Research Lab comments in his blog on the Comet ISON Observing Campaign web site: "The evidence appears strong that at some point approaching perihelion Comet ISON likely began to completely fall apart. What remains of ISON now is going to be either just a cloud of dust, or perhaps a few very depleted chunks of nucleus. Either way, it's not going to flare up at this point and we should assume the comet's show is over."

Every night, a network of NASA all-sky cameras scans the skies above the United States for meteoritic fireballs. Automated software maintained by NASA's Meteoroid Environment Office calculates their orbits, velocity, penetration depth in Earth's atmosphere and many other characteristics. Daily results are presented here on Spaceweather.com.

In this diagram of the inner solar system, all of the fireball orbits intersect at a single point--Earth. The orbits are color-coded by velocity, from slow (red) to fast (blue). [Larger image] [movies]

Near Earth Asteroids

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.